Birmingham Small Arms Company

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Birmingham Small Arms Company Ltd. share dated July 18, 1930
BSA from 1920
BSA Golden Flash (late 1950s)

The Birmingham Small Arms Company , or BSA for short , is a British motorcycle manufacturer and former automobile, bicycle and arms manufacturer in Birmingham , England .


BSA was founded in 1861 out of fourteen gunsmiths who had already merged as the Birmingham Small Arms Trade Association , England. This association supplied arms to the British government during the Crimean War of 1853-1856.

The company started new branches after the arms trade worsened. The production of bicycles began in the 1880s, and in 1903 the company's first test motorcycle was designed.

The first prototype of an automobile was produced in 1907. The company sold 150 automobiles in the next year.

From 1909, BSA offered a range of motorcycles for sale. In 1910 the company acquired the British Daimler Motor Company in order to equip their automobiles with their engines.

First World War

During the First World War , the company turned back to arms production and expanded its business areas. BSA produced rifles and the Lewis machine gun, but also grenades, motorcycles and other vehicles for this war.

Between the world wars

In 1920 the group acquired the estate of the short-lived aircraft manufacturer Airco and in 1931 the automobile manufacturer Lanchester . In the 1930s, the board of directors decided to put the armaments machine tools that had been in storage since the First World War back into operation. These had been stored in the company at their own expense, in the hope that BSA would again be in demand as a patriotic armaments manufacturer.

BSA was particularly successful with the construction of heavy single-cylinder motorcycles, the "M" series. The M20 / 21/22 were all side-steered single cylinders. Later there were also models with valves hanging in the head ( OHV ).

BSA motorcycles were exported to large parts of the world and were considered very reliable.

Second World War

During World War II, BSA owned 67 factories and was well positioned to supply rifles and ammunition. BSA also produced under license. During the war, they produced over 1 million Lee Enfield rifles and half a million Browning machine guns . War production also included the manufacture of motorcycles. BSA delivered 126,000 M20 motorcycles to the armed forces, from 1937 and later until 1950 additional military bicycles including the paratrooper bicycle. At the same time, the Daimler Motor Company was producing armored cars.

After the Second World War

In 1954 a three-wheeled automobile was created as a prototype.

1956 was the last time there was a "Lanchester" brand. The Lanchester company was taken over by Jaguar in 1960 together with Daimler .

After the Second World War, British diplomats took plans for the DKW RT 125, which is very popular in Germany, to England to compensate for the damage they had suffered . At BSA, an almost identical model, the BSA Bantam, was manufactured for a long time according to these original plans.

When you talk about BSA motorcycles these days, the term “Gold Star” comes up automatically. The BSA DBD 34 Goldstar was a large-volume single-cylinder motorcycle that was also able to achieve considerable success in racing.

In the early 1950s, BSA took over competitor Triumph. Interestingly, the company was run from Triumph. Single-cylinder machines developed by Triumph were also sold as BSA.

In the mid-1940s, BSA increasingly built compact two-cylinder engines. The classic English twin with a 360 ° crank pin offset was produced as the BSA A7 with 500 cm³ from 1946 and as the A10 with 650 cm³ displacement from 1949, first with a rigid frame, later with swing chassis. These models were particularly successful in the USA . They were available in a tame design suitable for everyday use, but also with a sporty character in various tuning levels. As was customary at the time, the gearboxes were housed separately in a separate housing. The so-called "pre-unit" models (with separate engine and gearbox) were replaced in 1962 by the A50 (500 cm³) and the A65 (650 cm³). The new models had so-called "unit" motors in block motor design with motor and gearbox in one housing. The engine design changed significantly. While the A7 and A10 were still classic British twins with a long stroke, the new models were designed with a short stroke. This was not well received by customers. At the end of the series there was a small series of Twins with 750 cc displacement in 1971, the A70. these went exclusively to the USA. As the final stage of development, a three-cylinder motorcycle developed by Triumph, the A75 Rocket 3, was brought onto the market in 1968. As a result of an outdated styling, the sales figures for this machine remained modest. In addition, the production costs for this model were so high that it hardly made any profit despite the high price. BSA has long been the world's largest manufacturer of motorcycles. At the end of the 1960s to the beginning of the 1970s, however, sales figures plummeted as a result of an incorrect and sharply criticized model policy. The models of BSA and Triumph became more and more similar (BSA Rocket3 / Trident; BSA A65 Oil in Frame / Triumph T120 Oil in Frame) and with the model year 1972 BSA stopped the motorcycle production forever. Triumph lasted a little longer and temporarily merged with the last remaining British motorcycle brand Norton in the Norton Villiers Triumph (NVT) group.

BSA today

After several changes of ownership, the brand name is now owned by the BSA Regal Group . It mainly produces spare parts for motorcycles.

Furthermore, there is a fan base all over Europe and in the USA, especially the British classic motorcycles with 650 cm³ from the 1960s, which were very fast for their time, when BSA, Triumph and Norton built the sportiest motorcycles in the world before the Japanese began to build motorcycles to dominate.

Several hundred BSA with sidecars (mostly B31, B32 and B40, but also some 500cc models) are still in use today (2009) as public transport (“Becak”) in the Indonesian city ​​of Pematang Siantar (North Sumatra). Since there is no spare parts supply, most of them are very individual and modified and repaired.

In 2016, the Indian vehicle manufacturer Mahindra & Mahindra took over the brand rights and promised to produce motorcycles again under the name within two years. However, the restart has not taken place until today (August 2020).

Thread size BSA

The abbreviation BSA of the formerly most important British arms manufacturer and later bicycle and motorcycle manufacturer lives on worldwide as the common name for the most widely used thread size for bicycle inner bearings . The company developed the measure for their bikes. The standard size was first introduced by BSA and ultimately led by the mass of British bicycle manufacturers under the name British Standard Cycle (BSC). The thread size first caught on in Great Britain and was included in the British Standards . These standards are now part of the ISO standard .

The dimension indicates a diameter of 1.375 inches (34.9 mm) × 24 tpi (turns per inch) inner bearing threads. The thread sits on the left side of the fixed bearing shell . The BSA thread established itself as the standard because it has the technical advantage that the thread tends to "kick in" the bearing due to the thread turn in the treading direction. The competing "Italian thread" (ITA 36 × 24 tpi) has a right-hand thread on both sides, which means that the bearing shells on the left side of the frame loosen more easily due to the force applied in the direction of treading.

BSA threewheeler from 1932
BSA Ten 6-Light Saloon from 1934
BSA Scout Sports tourer from 1936

Automobile models

model construction time cylinder Displacement wheelbase
14/18 hp 1907-1910 4 row 2596 cc 2591 mm
18/23 hp 1908-1910 4 row 3622 cc 2896 mm
25/30 hp 1908-1911 4 row 5401 cc 3150 mm
15/20 hp 1910-1911 4 row 3053 cc 2667 mm
20/25 hp 1910-1911 4 row 4156 cc 2896 mm
13.9 hp 1912-1915 4 row 2015 cm³ 2756-2845 mm
10 hp 1921-1924 2 V 1080 cc 2438 mm
11 hp 1923 4 row 1468 cc 2692 mm
12 hp 1923 4 row 1028 cc 2819 mm
14 hp 1924 4 row 1765 cc 2438-2692 mm
16 hp 1924-1926 6 row 1872 cc 2972 mm
9 hp 1932-1935 2 V 1021 cc 2299 mm
10 hp 1933-1936 4 row 1185 cc 2477 mm
FWD 1933-1936 4 row 1075 cc 2299-2743 mm
Light 6 1935-1936 6 row 1378 cc 2515 mm
IOH 1936 4 row 1330 cc 2515 mm
Scout 1937-1939 4 row 1204 cc 2286-2426 mm


  • David Culshaw & Peter Horrobin: The Complete Catalog of British Cars 1895–1975. Veloce Publishing plc., Dorchester 1999, ISBN 1-874105-93-6 .

Web links

Commons : BSA  - collection of images, videos and audio files

Individual evidence

  1. Walter Drawer: Small Cars International. Motorbuch-Verlag, Stuttgart 1999.
  2. Photo by TrekEarth
  3. Indians bring back cult brand. In: August 23, 2019, accessed August 4, 2020 .